The swimming pool is open when the high temperature is higher than 20 degrees celcius. Lainey tried to swim on Monday and Thursday (which was 33 days later). The pool was open on Monday, but it was closed on Thursday. The high temperature was 30C on Monday, but decreased at a constant rate in the next 33 days. Write an inequality to determine the rate of temperature decrease in degrees Celsius per day, d, from Monday to Thursday.

Question

Mercury · Answer

The swimming pool is open when the high temperature is higher than 20 degrees celcius.
The pool was open on Monday, but it was closed on Thursday.

- so from that info, the pool must have been at least 20 degrees C on Monday, but less than 20 on Thursday.

the temperature decreased from 30 degrees at a constant rate in the next 33 days.
- so, if the temp. decreased at a rate of "r" degrees per day, then the total decrease across 33 days is 33r
subtract this from the initial temperature

temperature after decrease = 30 - 33r

from there, set up the inequality: "the temperature after decrease is less 20" ---> translate this into an inequality